The present invention relates to binding machines.
Binding machines for binding stacks of sheets are known. The machines include a punching mechanism for punching the stack of sheets to be bound, and a binding apparatus for binding the punched stack of sheets. Various types of binding elements can be used with the binding apparatus, including elements typically referred to as “comb” binding elements.
FIG. 1 illustrates a prior art GBC COMBBIND C340 binding machine 10 having a manually-actuated punching device. A user rotates the lever or handle 14 to punch the holes in the stack of sheets to be bound, which is positioned in a slot 18. The binding machine 10 includes a punch plate having thereon a plurality of punch pins (e.g., 19 or 21 pins) that pierce the stack of sheets as the punch plate is moved by operation of the handle 14.
Prior art binding machines, including the illustrated binding machine 10, typically require a large input of force by the user to punch the stack of sheets. In addition to requiring a large force input, the user will experience a rough and uneven motion of the handle 14 along the punch stroke, as the punching force changes significantly during the punching stroke. This is due to the variation in force required to pierce the stack of sheets as the different punch pins strike and pierce the stack of sheets.
FIG. 2 is a graph illustrating the punch force versus displacement for the punch plate (including all of the punch pins), which was mathematically determined based on test data collected for a single punch pin of the prior art binding machine 10. Alternatively, the graph can be obtained using test data collected for the entire punch plate (i.e., test data taken for the punch plate with all of punch pins). This graph can be referred to as the punch force profile for the punch plate. The force value is not normalized, but merely includes a generic scale for reference. The noticeable peaks and valleys are evidence of the changes in punch force occurring during the punch stroke as various punch pins strike, pierce, and pass through the stack of sheets. As the punch pins on the punch plate vary in length, different pins strike and pierce the stack of sheets at different times during the punch stroke. These peaks and valleys shown in the graph explain the rough and uneven movement of the handle 14 experienced by the user during the punch stroke. At one location at about the midpoint of the punch stroke where the force trend line is generally flat, designated as portion 22 in FIG. 2, a percentage change in force from a peak 26 to a valley 30 is about 29 percent. At other locations along the punch stroke, the percentage change in force between peaks and valleys is significantly higher. It is believed that this graph in FIG. 2 is representative of prior art binding machines, which require significant peak force input, but also have a very rough and uneven punch stroke, the force and vibration of which are transmitted through the handle 14 to the user to provide a very disjointed and rough operational feel.